Polarized Dispersion of X-rays in Pyrite

Diffraction of synchrotron radiation in a crystal of FeS₂ reveals dipolar anisotropy of anomalous scattering by Fe near its K-absorption edge, in spite of the almost-regular octahedral geometry of the nearest S neighbors. At 7121 eV, the magnitude of f changes with polarization direction by as much as 0.7 electron units. No effects of quadrupolar anisotropy were detected.